Cost effectiveness of imatinib mesylate in the treatment of advanced gastrointestinal stromal tumours

Cost-Effectiveness Analysis of Tyrosine Kinase Inhibitors in Gastrointestinal Stromal Tumor: A Systematic Review

Background: The introduction of tyrosine kinase inhibitor (TKI) therapy has dramatically improved the clinical effectiveness of patients with locally advanced and/or metastatic gastrointestinal stromal tumors (GIST), and this systematic review was conducted aiming at the cost-effectiveness analysis of TKIs in GIST.

Methods: A thorough literature search of online databases was performed, using appropriate terms such as “gastrointestinal stromal tumor or GIST,” “cost-effectiveness,” and “economic evaluation.” Data extraction was conducted independently by two authors, and completeness of reporting and quality of the evaluation were assessed. The systematic review was conducted following the PRISMA statement.

Results: Published between 2005 and 2020, 15 articles were incorporated into the systematic review. For advanced GIST, imatinib followed by sunitinib was considered cost-effective, and regorafenib was cost-effective compared with imatinib re-challenge therapy in the third-line treatment. For resectable GIST, 3-year adjuvant imatinib therapy represented a cost-effective treatment option. The precision medicine-assisted imatinib treatment was cost-effective compared with empirical treatment.

Conclusion: Although identified studies varied in predicted costs and quality-adjusted life years, there was general agreement in study conclusions. More cost-effectiveness analysis should be conducted regarding more TKIs that have been approved for the treatment of GIST.

Systematic Review Registration:https://www.crd.york.ac.uk/, PROSPERO: CRD42021225253.

Cost-Effectiveness Analysis of Fourth- or Further-Line Ripretinib in Advanced Gastrointestinal Stromal Tumors

Background

The INVICTUS trial assessed the efficacy and safety of ripretinib compared with placebo in the management of advanced gastrointestinal stromal tumors.

Method

We used a Markov model with three health states: progression-free disease, progression disease and death. We parameterized the model from time-to-event data (progression-free survival, overall survival) of ripretinib and placebo arms in the INVICTUS trial and extrapolated to a patient’s lifetime horizon. Estimates of health state utilities and costs were based on clinical trial data and the published literature. The outcomes of this model were measured in quality-adjusted life-years (QALYs), costs, and incremental cost-effectiveness ratios (ICERs). Uncertainty was tested via univariate and probabilistic sensitivity analyses.

Results

The base-case model projected improved outcomes (by 0.29 QALYs) and additional costs (by $70,251) and yielded an ICER of $244,010/QALY gained for ripretinib versus placebo. The results were most sensitive to progression rates, the price of ripretinib, and health state utilities. The ICER was most sensitive to overall survival. When overall survival in the placebo group was lower, the ICER dropped to $127,399/QALY. The ICER dropped to $150,000/QALY when the monthly cost of ripretinib decreased to $14,057. Probabilistic sensitivity analyses revealed that ripretinib was the cost-effective therapy in 41.1% of simulations at the willingness-to-pay (WTP) threshold of $150,000.

Conclusion

As the fourth- or further-line therapy in advanced gastrointestinal stromal tumors, ripretinib is not cost-effective in the US. Ripretinib would achieve its cost-effectiveness with a price discount of 56% given the present effectiveness.

Treatment of gastrointestinal tumor (GIST) of the rectum requiring abdominoperineal resection following neoadjuvant imatinib: a cost-effectiveness analysis

Background

Neoadjuvant imatinib for gastrointestinal stromal tumors (GIST) of the rectum can reduce, but may not eliminate, risk of surgical morbidity from permanent bowel diversion. We sought to evaluate the cost-effectiveness of alternative strategies in rectal GIST patients requiring abdominoperineal resection following neoadjuvant imatinib.

Methods

We developed a Markov model using a healthcare payers' perspective to estimate costs in 2017 Singapore dollars (SGD) and quality adjusted life years (QALYs) for upfront abdominoperineal resection (UAPR) versus continued imatinib until progression (CIUP) following 1 year of neoadjuvant imatinib. Transition probabilities and utilities were obtained from published data, and costs were estimated using data from the National Cancer Centre Singapore. Deterministic and probabilistic sensitivity analyses were conducted to probe model uncertainty. Incremental cost-effectiveness ratio below SGD 50,000 per QALY gained was considered cost-effective.

Results

In the base case, UAPR dominates CIUP being both more effective (8.66 QALYS vs 5.43 QALYs) and less expensive (SGD 312,627 vs SGD 339,011). These estimates were most sensitive to 2 variables, utility of abdominoperineal resection and annual recurrence probability post-abdominoperineal resection. However, simultaneously varying the values of these variables to maximally favor CIUP did not render it the more cost effective strategy at willingness to pay (WTP) of SGD 50,000. In probabilistic sensitivity analysis, UAPR had probability of being cost-effective compared with CIUP greater than 95%, reaching 100% at WTP SGD 10,000.

Conclusion

UAPR is more effective and less costly than CIUP for patients with rectal GIST requiring abdominoperineal resection following neoadjuvant imatinib, and is the strategy of choice in this setting.

Economic Evaluations of Pharmaceuticals Granted a Marketing Authorisation Without the Results of Randomised Trials: A Systematic Review and Taxonomy

BACKGROUND

Pharmaceuticals are usually granted a marketing authorisation on the basis of randomised controlled trials (RCTs). Occasionally the efficacy of a treatment is assessed without a randomised comparator group (either active or placebo).

OBJECTIVE

To identify and develop a taxonomic account of economic modelling approaches for pharmaceuticals licensed without RCT data.

METHODS

We searched PubMed, the websites of UK health technology assessment bodies and the International Society for Pharmacoeconomics and Outcomes Research Scientific Presentations Database for assessments of treatments granted a marketing authorisation by the US Food and Drug Administration or European Medicines Agency from January 1999 to May 2014 without RCT data (74 indications). The outcome of interest was the approach to modelling efficacy data.

RESULTS

Fifty-one unique models were identified in 29 peer-reviewed articles, 30 health technology appraisals, and 15 International Society for Pharmacoeconomics and Outcomes Research abstracts concerning 30 indications (44 indications had not been modelled). We noted the high rate of non-submission to health technology assessment agencies (28/98). The majority of models (43/51) were based on 'historical controls'-comparisons to previous meta-analysis or pooling of trials (5), individual trials (16), registries/case series (15), or expert opinion (7). Other approaches used the patient as their own control, performed threshold analysis, assumed time on treatment was added to overall survival, or performed cost-minimisation analysis.

CONCLUSIONS

There is considerable variation in the quality and approach of models constructed for drugs granted a marketing authorisation without a RCT. The most common approach is of a naive comparison to historical data (using other trials/registry data as a control group), which has considerable scope for bias.

The timing and probability of treatment switch under cost uncertainty: an application to patients with gastrointestinal stromal tumor

BACKGROUND

Cost fluctuations render the outcome of any treatment switch uncertain, so that decision makers might have to wait for more information before optimally switching treatments, especially when the incremental cost per quality-adjusted life year (QALY) gained cannot be fully recovered later on.

OBJECTIVE

To analyze the timing of treatment switch under cost uncertainty.

METHODS

A dynamic stochastic model for the optimal timing of a treatment switch is developed and applied to a problem in medical decision taking, i.e. to patients with unresectable gastrointestinal stromal tumour (GIST).

RESULTS

The theoretical model suggests that cost uncertainty reduces expected net benefit. In addition, cost volatility discourages switching treatments. The stochastic model also illustrates that as technologies become less cost competitive, the cost uncertainty becomes more dominant. With limited substitutability, higher quality of technologies will increase the demand for those technologies disregarding the cost uncertainty. The results of the empirical application suggest that the first-line treatment may be the better choice when considering lifetime welfare.

CONCLUSIONS

Under uncertainty and irreversibility, low-risk patients must begin the second-line treatment as soon as possible, which is precisely when the second-line treatment is least valuable. As the costs of reversing current treatment impacts fall, it becomes more feasible to provide the option-preserving treatment to these low-risk individuals later on.

Mean overall survival gain with aflibercept plus FOLFIRI vs placebo plus FOLFIRI in patients with previously treated metastatic colorectal cancer. Br J Cancer. 2013;109:1735-1743. [PMID: 24045663 PMCID: PMC3790175 DOI: 10.1038/bjc.2013.523]

BACKGROUND

Mean survival in cancer trials can be estimated with statistical techniques to extrapolate study survival curves. This methodology was applied to data from the VELOUR trial, where use of the novel biologic aflibercept (ziv-aflibercept in the United States) in combination with fluorouracil+leucovorin+irinotecan (FOLFIRI), had significantly increased median overall survival (OS) by 1.44 months, vs placebo plus FOLFIRI in patients with metastatic colorectal cancer (mCRC) resistant to, or that had progressed following, an oxaliplatin-containing regimen.

METHODS

Parametric survival analyses were used to identify distributions with the best fit to the empirical VELOUR data. Mean OS for the two treatment groups (and pre-defined subgroups) was calculated from the fitted curves over a 15-year survival period.

RESULTS

Overall, the log-logistic distribution was the best-fitting for both treatment arms and, with it, the estimated difference in mean OS over 15 years between aflibercept+FOLFIRI and placebo+FOLFIRI was 4.7 months. In addition, the survival advantage with aflibercept was at least 3 months for the ITT population, whichever distribution was used to extrapolate survival.

CONCLUSION

Extrapolation of survival curves suggests the mean OS difference for aflibercept in the VELOUR trial is at least 3 months in the ITT population and selected subgroups.

Cost-effectiveness of 3-years of adjuvant imatinib in gastrointestinal stromal tumors (GIST) in the United States

BACKGROUND

Recent clinical trial data have demonstrated that 3 years vs 1 year of adjuvant imatinib therapy for patients with surgically resected Kit+ Gastrointestinal Stromal Tumors (GIST) leads to a significant improvement in recurrence-free survival and overall survival. This study assesses the cost-effectiveness of treating patients with 3 years vs 1 year of imatinib from a US payer's perspective.

METHODS

A Markov model was developed to predict GIST recurrence and treatment costs. Patients enter the model after surgery and transition among three health states: free of recurrence, recurrence, and death. Recurrence, mortality, costs, and utilities were derived from clinical trial and published literature. Expected costs and quality-adjusted life years (QALYs) were estimated and discounted at 3%/year. Deterministic and probabilistic sensitivity analyses were conducted.

RESULTS

Patients receiving 3 years of imatinib had higher QALYs (8.53 vs 7.18) than those receiving 1 year of imatinib. Total lifetime per-patient cost was $302,100 for 3 years vs $217,800 for 1 year of imatinib. Incremental cost effectiveness ratio of 3 years vs 1 year of imatinib was $62,600/QALY. Model results were sensitive to long-term rate of GIST recurrence (beyond 5 years) and cost of imatinib. At a threshold of $100,000/QALY, 3 years vs 1 year of imatinib was cost-effective in 100% of simulations.

LIMITATIONS

The model is a simplified representation of disease natural history and may not account for all possible health states and complications associated with disease. Resource utilization on treatment was estimated using the resource use data from previous trials, therefore calculated medical costs might be over-estimated compared to the real-world setting.

CONCLUSIONS

Model results suggest that treatment with 3 years vs 1 year of imatinib is cost-effective at a $100,000/QALY threshold. Clinical and economic results suggest treating surgically resected Kit+ GIST patients with 3 years of imatinib would result in improved quality-adjusted survival.

Clinical experience in diagnosis and treatment of malignant gastrointestinal stromal tumors

This study investigated the clinical pathologic character of malignant gastrointestinal stromal tumors (MGIST), their treatment with surgery, and evaluated the efficacy of imatinib postoperation. A total of 68 MGIST patients were enrolled. Of these, 27 patients underwent imatinib auxiliary therapy (treatment group) and 41 underwent imatinib therapy (control group). The therapeutic effects on the two groups were compared using χ(2) test analysis after follow-up of two years. The expressions of CD117, CD34, S100, Vimentin, and alpha smooth-muscle actin (SMA) were detected by immunohistochemistry methods. Of the 68 cases, 28 showed potential MGIST, whereas 40 had MGIST. Haemorrhagia or necrosis, abundant cell, manifest heteromorphism, and caryocinesia were observed in varying degrees. The positive rates of CD117, CD34, Vimentin, S100, and SMA were 89.7% (61/62), 88.2% (60/62), 73.5% (50/62), 41.1% (28/62) and 25.0% (17/62), respectively. The recurrence rate in the treatment group was significantly lower than that in the control group (p < 0.01). We concluded that CD117 and CD34 may be the most valuable markers in the diagnosis of MGIST, and the diagnosis of MGIST depends on the pathology. Surgery is a far better approach in the treatment of such patients, and imatinib is the more efficient target drug in preventing recurrence and metastasis.

Incorporation of adjuvant therapy into the multimodality management of gastrointestinal stromal tumors of the stomach in the United States

BACKGROUND

Gastrointestinal stromal tumors (GIST) treatment changed considerably with introduction of imatinib in 2001 and reports of early successes. However, little is known about imatinib incorporation into practice. Our objective was to examine the integration of adjuvant systemic therapy into GIST management.

METHODS

Patients with gastric GIST were identified (n = 4508) from the National Cancer Data Base (2001-2007). Separate regression models were developed to examine factors associated with adjuvant and neoadjuvant therapy use.

RESULTS

A total of 3050 patients underwent surgical resection. From 2001-2003 to 2006-2007, use of adjuvant therapy increased from 29 to 47% (P < 0.001). Patients were less likely to receive adjuvant therapy if tumors were <3 cm, low grade, had negative margins, were treated at low-volume centers, or were diagnosed during 2001-2003 (P < 0.01). Adjuvant systemic therapy for lesions <3 cm also increased (17 to 25%, P = 0.001). For high-risk GISTs, adjuvant therapy use increased from 41 to 58% overall, with increases of 46 to 70% at high-volume centers and 40 to 48% at low-volume centers (P < 0.001). Neoadjuvant therapy increased from 0 to 8%; patients were more likely to receive neoadjuvant treatment if their tumor was >6 cm, treated at high-volume centers, or were diagnosed during 2006-2007 (P < 0.001).

CONCLUSIONS

Adjuvant systemic therapy use for GISTs was increasing and widespread prior to FDA approval of adjuvant imatinib, suggesting that contemporaneous advances in management of advanced GIST were being simultaneously and rapidly translated into the adjuvant setting. As relatively costly therapies are integrated into practice, more robust tracking systems are needed to monitor the incorporation of new treatments.

Government use licenses in Thailand: an assessment of the health and economic impacts

BACKGROUND

Between 2006 and 2008, Thailand's Ministry of Public Health (MOPH) granted government use licenses for seven patented drugs in order to improve access to these essential treatments. The decision to grant the government use licenses was contentious both within and beyond the country. In particular, concerns were highlighted that the negative consequences might outweigh the expected benefits of the policy. This study conducted assessments of the health and economic implications of these government use licenses.

METHODS

The health and health-related economic impacts were quantified in terms of i) Quality Adjusted Life Years (QALYs) gained and ii) increased productivity in US dollars (USD) as a result of the increased access to drugs. The study adopted a five-year timeframe for the assessment, commencing from the time of the grant of the government use licenses. Empirical evidence gathered from national databases was used to assess the changes in volume of exports after US Generalized System of Preferences (GSP) withdrawal and level of foreign direct investment (FDI).

RESULTS

As a result of the granting of the government use licenses, an additional 84,158 patients were estimated to have received access to the seven drugs over five years. Health gains from the use of the seven drugs compared to their best alternative accounted for 12,493 QALYs gained, which translates into quantifiable incremental benefits to society of USD132.4 million. The government use license on efavirenze was found to have the greatest benefit. In respect of the country's economy, the study found that Thailand's overall exports increased overtime, although exports of the three US GSP withdrawal products to the US did decline. There was also found to be no relationship between the government use licenses and the level of foreign investment over the period 2002 to 2008.

CONCLUSIONS

The public health benefits of the government use licenses were generally positive. Specifically, the policy helped to increase access to patented drugs, while the impact of the US GSP withdrawal did not adversely affect the overall export status. Because the levels of benefit gained from the government use licenses varied widely between the seven drugs, depending on several factors, this study makes recommendations for the future implementation of the policy in order to maximise benefits.

Advances in cancer therapeutics and patient access to new drugs

Globally, there are approximately 7.4 million cancer deaths annually, approximately 13% of deaths from all causes. Cancer is a disease of older people and, as the population ages over the next 10-20 years, we can expect an increase in the cancer incidence. Encouragingly, cancer mortality has stabilized in many countries. Part of this success may be attributed to the development of new cancer agents, collectively called 'targeted therapies', that are more specific to key components of tumour growth. Worldwide, however, one of the main factors that limit patient access to these important new drugs is their cost, which is higher than traditional chemotherapy. In this review, the clinical and pharmacoeconomic data of selected targeted agents are discussed. In the second part of this article, the challenges faced by healthcare systems in making such drugs available to patients is reviewed. Current strategies used by many countries around the world to manage cancer drug budgets are presented, along with a proposed approach using pharmacoeconomic methodology that may increase patient access.

Cost effectiveness of tyrosine kinase inhibitor therapy in metastatic gastrointestinal stromal tumors

BACKGROUND

Tyrosine kinase inhibitors (TKIs) such as imatinib mesylate have revolutionized the treatment of primary unresectable and/or metastatic gastrointestinal stromal tumors (GISTs), providing durable disease control and extended survival. Although most patients eventually progress on therapy, dose escalation has been shown to benefit some patients. Sunitinib, a multitargeted kinase inhibitor is effective against imatinib-resistant or intolerant GIST patients. Although the cost of TKI therapy in GIST is high, no other effective systemic treatment options exist.

OBJECTIVE

Review pharmacoeconomic studies to determine the cost effectiveness (CE) of 1st- and 2nd-line TKI therapies in GIST.

METHODS

A literature review using Medline and PubMed databases was conducted to identify published economic analyses of TKI therapy in GIST. Key results from these studies were analyzed.

RESULTS

Six pharmacoeconomic studies were identified, including three analyses of 1st-line imatinib and three analyses of 2nd-line sunitinib. These studies employed various time horizons and discount rates and modeled CE from a number of different perspectives. Most of the pharmacoeconomic studies reviewed used survival as their efficacy endpoint, projecting outcomes beyond available data to model CE. Analyses of 2nd-line sunitinib using survival additionally faced the challenge of adjusting for the effect of placebo crossover to active treatment in the pivotal phase III study. Most studies used Markov techniques with a range of transition probabilities.

CONCLUSIONS

Published pharmacoeconomic studies of 1st- and 2nd-line TKI therapy for advanced GIST employ various time horizons, discount rates, and different CE models. Consequently, these differences make comparisons between studies difficult. Studies of 1st-line imatinib concluded that imatinib was cost effective in advanced, metastatic GIST. Likewise, based on data reviewed here, 2nd-line sunitinib appears to be cost effective in patients with advanced GIST who are intolerant/resistant to imatinib. Key limitations of this review included inconsistency among the studies evaluated with regard to methodologies, countries of origination (currency and healthcare systems), and patient demographics.

Imatinib mesilate for the treatment of gastrointestinal stromal tumour

BACKGROUND

The molecular hallmark of gastrointestinal stromal tumours (GISTs), the mutation of the KIT gene, was discovered 10 years ago. GISTs have since been recognized as separate pathological entities among sarcomas, and have become a model for targeted treatment of solid tumours. Imatinib mesilate, which was approved in 2002 for the treatment of patients with advanced GIST, has dramatically changed the course of the disease.

OBJECTIVE

This article will focus on the development of imatinib mesilate in the treatment of patients with GIST.

METHODS

A Pubmed search was performed using the keywords 'imatinib', 'gastrointestinal stromal', 'GIST', 'KIT' and 'PDGFR'. Websites of the American Society of Clinical Oncology and the European Society of Medical Oncology were searched for data reported in abstract form at recent symposiums. Personal communications from opinion leaders were sought for additional information that might be relevant.

RESULTS

Imatinib has changed the clinical course of patients with advanced GISTs and further development in the adjuvant setting as well as prospective assessment of predictive factors are the current focus of ongoing research.